Distinct Phases of Repetitive Activity During Atrial Fibrillation in Sheep Atria: High Density Mapping Study

Abstract

Introduction: Mapping and temporal evolution of atrial fibrillation (AF) remains poorly understood. We aimed to characterise wavefront propagation during AF in an ovine hypertensive model. Methods: Electrical activity during induced AF on the epicardial surface of the left (LA) and right (RA) atria was recorded in vivo using rectangular meshes of electrodes in 11 sheep with an established model of hypertension (1K1C). Trajectory of the wave propagation was reconstructed and used to classify each distinct propagation event. Periods of activity with repetitive wave trajectory were defined as phases of arrhythmia. Results: 9241 distinct activation events in total were analysed. LA had greater than RA ratio of centrifugal activations (41% vs. 0.005%) and wave collisions (7.6% vs. 0.01%). RA had greater ratio of passing waves (88% vs. 51%), rotating waves (0.01% vs. 0%), total conduction blocks (0.001% vs. 0%) and waves circumventing conduction block (0.08% vs. 0%). With relation to anatomical characteristics, 15 distinct phase types were identified in each atria. The most frequent transition in RA was a transition between reentrant phase and phase of waves coming from coronary sinus region (CS) (21%). In LA, the most frequent transitions were between phase of waves train coming from Bachman-Bundle (BB) and phase of interaction between waves coming from BB and CS direction (12%). Conclusion: High density mapping of wavefront trajectory during AF provides new insights into arrhythmia dynamics. The most frequent transition between phases of AF in ovine sheep model is transition in RA between reentrant activity and wave train coming from CS. It points to an important interaction between CS and reentrant activity which may have important implications in AF mapping and treatment.